Seal ring and use of this ring

ABSTRACT

A sealing ring is provided for mounting in a sealing groove in each pipe-joint half of a pipe joint for high pressure use. The sealing ring comprises two joined bodies having bevelled outer sections. The sealing ring is configured such that the joined bodies are compressed toward each other upon insertion into the sealing groove of each pipe-joint half. The two joined bodies are separated by an integrated distancing piece which has an aperture that extends therethrough and is substantially perpendicular to the middle plane of the sealing ring.

FIELD OF THE INVENTION

The present invention relates to a seal ring for conduit flanges and-joints which have to withstand high pressure and possibly thermal andmechanical loads. A special field of application for this kind of sealsis found in risers in the oil industry.

BACKGROUND OF THE INVENTION

In high pressure technology there are several known types of seal ringsfor conduit joints. Common to all of these is the fact that they aremade of compact and non-compressible material like metal and metalalloys since other types of material will not be as strong as requiredin high pressure technology.

The disadvantage of using such conventional seal rings and gaskets, isthe fact that the joints in the pipeline typically are exposed tothermal work in the material as well as mechanical stress forcesresulting in a joint which after some time will start leaking.Furthermore, when using this kind of joints and gaskets it has so farnot been possible to check the seal capacity of such conduit joints,especially not during assembly, without resorting to test methods whichare both demanding and expensive. Another disadvantage of conventionaltypes of gaskets is the fact that they provide flexibility in onedirection only, which is insufficient in order to ensure proper sealcapacity.

A purpose of the present invention is thus to provide a seal ringavoiding the aforementioned problems in connection with work in thematerial in the area around the conduit joints, whilst testing of theconduit joints in joined pipelines is enabled, the testing being carriedout with full pressure in the pipeline.

BRIEF DESCRIPTION OF THE DRAWING

In the following the invention will be explained referring to theattached drawings in which:

FIG. 1 is a view of a conventional conduit joint with a flange,

FIG. 2 is a view of an embodiment of a seal ring according to thepresent invention,

FIG. 3 is a view of one half of such a flange with a marked entrance fora pressure probe for the testing of the seal performances of the flangeand the conduit joint when exposed to high pressure.

FIG. 4 is a section of a groove in a seal ring according to theinvention.

FIG. 5 illustrates another type of flange assembled with a sealaccording to the invention.

FIG. 6 illustrates a third type of flange assembled with a sealaccording to the invention.

FIG. 7 and 8 illustrate in section two types of flanges assembled arounda conduit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Today it is both common and necessary to incorporate a seal in conduitjoining flanges to ensure a leakage proof joint. As explained above itis however typical that such seals are shaped so as to achieve anaccurate fitting in the corresponding groove in the flange, and furtherthat they are made of compact material, causing the seal to startleaking after some time because of mechanical and thermal wear and tearas well as work from the material surrounding the joint.

In addition it has earlier been necessary to carry out pressure tests onsuch joints and gaskets after complete assembly of the pipelines, and ithas not been possible to do these tests with a pressure below or aboveoperation pressure.

According to the invention it has been found to be advantageous to shapea seal like this so as to enable an individual fitting in the flangegroove, and particularly with flexibility in at least two directions.

In order to have the flange seal according to the invention functionaccordingly, the seal is shaped so as to include at least twoconfronting seal halves 1,2, which is distanced by a web 3 between thehalves 1,2. Because of the web 3 the seal will have a certain resilientcharacteristic in that the halves 1,2 are forced against each other whenmounted in a seal groove 31,41. Because of this it is very importantthat the seal flange is fitted relative to the groove 31,41 so that thehalves 1,2 are forced against each other when mounted, e.g. that theseal will rest against the material of the groove 31,41 when the seal ishalf way down in the groove. By giving the seal halves 1,2 apreferentially conic region in the end/peripheral region of the seal,this kind of fitting may be ensured. The groove may further be given apreferentially inward conic shape as is shown in FIG. 3 and 4.

To ensure good seal performances of the seal according to the invention,it is preferred that the cone angle between the outer plane surface 4 ofthe seal and the sloping part 5 of the seal is in the range 13,5°±0,5°,although other values of this angle may be applied. It is preferred thatthe degree of deformation resulting from the compression of the seal inthe conic groove 31,41 is in the range 0,041±0,01, i.e. with an openingof the groove equal to 19,533 mm the compression of the seal is 0,8mm±0,2 mm. This is however only a preferred ratio, and other ratios willbe available to the expert taking into consideration the intendedoperation of the seal as well as the characteristics of the material ofthe seal.

As mentioned above the present type of seal is intended for highpressure pipelines, e.g. pipelines with a pressure of 75 bar and above,A pressure of this magnitude is typically present in risers on oilplatforms, but it may also be found in other fields like for instance inprocess technology or in energy technology like nuclear power plants.With respect to process technology it will also be required to make theseals according to the invention from a material resistant to the mediumcarried in the pipeline. The person skilled in the art will have tochoose the material depending on the particular case. Examples ofmaterials suitable for most fields of application are metal and metalalloys like stainless steel, carbon steel, low-alloy steel, acidresistant steel or other metal alloys.

It will also be possible to use other types of material for the sealaccording to the invention, like ceramic material and/or compositematerial assuming that they have sufficient tension and sealingqualities corresponding to those demonstrated by the aforementionedtypes of metal. The person skilled in the art may naturally decide whatmaterials to use.

It will also be possible to shape a seal according to the inventiondifferently from what is shown in FIG. 2, for instance with a web 3which is either wider or more narrow than the one illustrated, bearingin mind that the resilient qualities of the seal parts 1,2 have to bemaintained. It will thus be less preferable to have the width of the web3 pass the transition between the plane section 4 and the conic section5. It is also obvious that the web 3 should not be to narrow, and anexample of the ratio between the total width of the seal and the widthof the web is 6,4, i.e. the total width may have a value equal to 25,4mm and the width of the web is then 4 mm. The values above relates toseals where the web is positioned around a centre line 7 of the seal,but it may also be shifted in one or the other direction with respect tothis centre line.

Similarly the groove 31,41 in the flange part will have to have a depthwhich is at least equal to half of the total length of the seal,preferably somewhat larger so as to achieve the compression effectmentioned above when the seal according to the invention is assembled.This is suggested in FIG. 5 and 6, referring to the gap 14 between thematerial in the flange halves 12 and 13 and the seal 11.

Beside mechanical and thermal loads, the seal according to the inventionwill also be able to absorb vibrations from the pipeline and the conduitjoints when shaped and mounted as explained.

To ensure that the flange halves 12 and 13 are sufficiently secured toeach other to form a sufficiently strong connection, the halves may forinstance be screwed together by bolts 15,15', like shown in FIG. 1, 5,6, 7 and 8. This securing may be carried out in a conventional way, butalso including a seal according to the present invention to ensure theaforementioned seal tightness.

FIG. 6 and 7 illustrate an embodiment of a conventional flange with aseal according to the present invention. To ensure sufficientcompression of the flange halves 12 and 13, the halves are shaped sothat a compression groove 16 is formed between the halves 12 and 13,resulting in an optimal compression when the nuts 15,15' are tightened.

The seal tightness explained above is a result of the fact that the sealaccording to the invention has at least one groove between the sealhalves 1 and 2. As an example a seal ring with two grooves isillustrated in FIG. 2, but it is obvious that one such groove may beapplied, depending on the field of use. It is also obvious that the sealring may be applied in horizontal as well as vertical conduit joints,and also in conduit joints with any arbitrary slope.

One particularly preferred embodiment of the seal ring according to theinvention includes at least one penetrating hole 6 through the web 3.The purpose of the hole 6 is to provide the possibility of performing apressure test on the tightness of the seal and thereby the conduit jointduring mounting, with a pressure at least equal to the total operationpressure. As explained above, previously this has not been possiblesince the seals have been made of compact material, and testing of theseal tightness has consequently only been possible by performingpressure tests from the inner surface of the pipeline, and these testshad to be carried out with a pressure substantially less than theoperation pressure. The dimension of the hole 6 is not critical, but ithas to be big enough to transport fluids with pressure, but on the otherhand not so big that it weakens the material in the web 3. An example ofan applicable dimension of the hole is 2/3 of the total width of the web3, but other dimensions may also be used.

The advantages of having the possibility of testing conduit jointsparticularly in risers during mounting and with total operationpressure, are obvious to the person skilled in the art.

The method for performing a pressure test of the conduit joints includesthe arrangement of a nozzle in a corresponding hole, indicated by anarrow in FIG. 3, so that the nozzle faces and ends at the bottom of thegroove 31. The hole may for instance be drilled into the flange. In thisway will it be possible to pressurize the groove 31 with an arbitrarypressure without having to pressurize the pipe line at all. Consequentlyany conduit joint may be pressure-tested separately. This positioning ofa relief hole will not have a negative influence on the flange, and itmay be plugged after a possible removal of the nozzle. The size of thehole may for instance be 3,2 mm, but other sizes are available to theperson skilled in the art and will not limit the inventive concept ofthe method for a separate pressure testing of the mounted flanges andseals.

In order to pressure test the overall seal tightness, it is importantthat a penetrating hole 6 is present in the web 3 so that the mediumapplied in the testing of the seal tightness has access to both sides ofthe seal in those cases where a seal with a shape like the oneillustrated in FIG. 2 is used.

The medium applied in the pressure test may be a fluid, for instance afluid corresponding to the one that will be present either inside of oroutside of the pipeline during operation. It will however be possible touse other types of media in the pressure testing of the conduit joint.

The present invention has been explained above referring to particularembodiments of the seal ring, but this will not limit the scope theinvention, as will be seen from the subsequent claims.

What is claimed is:
 1. A sealing ring for flange face to flange facemating of pipe joints in high pressure pipes for mounting completely ina sealing groove consisting of a flange groove in each pipe-joint half,said sealing ring comprising:two mutually joined bodies with bevelledouter sections wherein one-half of the sealing ring length is no greaterthan the depth of the sealing groove in each pipe-joint half, the joinedbodies of the sealing ring being mutually connected and separated fromeach other with an integrated distancing piece and configured such thatsaid joined bodies are compressed toward each other upon insertion intothe sealing groove; said distancing piece comprising at least onepenetrating aperture that extends substantially perpendicularly to themiddle plane of the sealing ring.
 2. Sealing ring according to claim 1,wherein the dimension of the penetrating aperture is about 2/3 of thetotal width of the distancing piece.
 3. Sealing ring according to claim1 wherein the sealing ring is a metal or a metal alloy.
 4. Sealing ringaccording to claim 1 wherein the sealing ring is a ceramic or acomposite material.
 5. A sealing ring according to claim 1 wherein thesealing ring is adapted for pressure-tight joining of pipe elements inrisers.
 6. A sealing ring according to claim 2 wherein the sealing ringis a metal or a metal alloy.
 7. A sealing ring according to claim 2wherein the sealing ring is a ceramic or a composite material.
 8. Asealing ring according to claim 2 wherein the sealing ring is adaptedfor pressure-tight joining of pipe elements in risers.
 9. A sealing ringaccording to claim 3 wherein the sealing ring is adapted forpressure-tight joining of pipe elements in risers.